Use ofCladophora glomerata to monitor heavy metals in rivers

Methods were developed for the use ofCladophora glomerata to monitor heavy metal concentrations in flowing waters. At least under conditions without marked fluctuations in ambient metal concentration, there was no detectable difference in the metal concentrations of young plants between terminal 2-cm lengths of filament and whole plants. In order to establish the relationship between metal concentration in plant and that in water, 60 algal and water samples were analyzed from sites in northern England for Fe, Cu, Zn, Cd and Pb. Other environmental variables were measured at the time in order to assess their influence on metal accumulation. There were highly significant correlations for each of the five metals between concentrations in alga and water. The regression equations relating metal in alga to metal in water permit an unknown environmental metal concentration to be estimated from the algal concentration. Multiple stepwise regression analyses were used to indicate environmental factors which may influence metal accumulation; for instance, Fe appears to have a positive influence on Cu accumulation. In generalCladophora accumulates much less metal than bryophytes, but the slope relating metal in alga to metal in water is steeper, particularly for Pb. This means thatCladophora is especially useful where there is a need for a sensitive indicator of differences between sites or sampling occasions.     

Accumulation of heavy metals in the metal-tolerant fern,Athyrium yokoscense,growing on various environments

The accumulation of copper, zinc and cadmium inA. yokoscense collected from Ashio (copper-contaminated area), Bandai (zinc- and cadmium-contaminated area) and Tama (non-contaminated area), has been investigated. Copper and zinc were accumulated most highly in the root, whilst cadmium was accumulated more in the leaf. The root ofA. yokoscense growing in areas contaminated with metals contained maximum amounts of Cu (5, 989 mg. kg⁻¹ dry weight) and Zn (6,384 mg.kg⁻¹ dry weight), while in the leaf from the Bandai area 164.8 mg Cd.kg⁻¹ dry weight was accumulated. These amounts are far greater than those found inA yokoscense growing on the non-metalliferous habitat (Tama). Twenty five times more zinc and three times more cadmium were found in the dead leaf than in the living leaf. InA. yokoscense growing on soils containing more than 1,000 mg Cu or Zn.kg⁻¹ dry weight, the uptake of copper by the root increased considerably with increasing copper content in the soils, while the uptake of zinc increased only slightly compared with the increase of zinc in the soils.     

Enteromorpha as a monitor of heavy metals in estuaries

An account is given of the use of Enteromorpha to monitor zinc, cadmium, mercury and lead pollution in six estuaries and the British North Sea coast. The ranges for each element were: Zn, 19–437 µg g^–1; µg g^–1 Cd, 0.07–4.8 µg g^–1; Hg, 0.02–0.23 µg g^–1. It is suggested that tissue analysis of Enteromorpha is one of the most useful biological techniques available in estuaries for pin-pointing aqueous (as opposed to sediment) metal contamination, and also for providing data suitable for world-wide comparisons. Provisional values are given for concentrations corresponding to moderate and high pollution.Deceased     

Accumulation of heavy metals by aquatic mosses. 3: Seasonal changes

The changes taking place at seven stream and river sites over a 14-month period were followed for the following:

1. % cover of Rhynchostegium riparioides;
2. relative abundance of Rhynchostegium as part of the whole plant community and, where present, also Amblystegium riparium and Fontinalis antipyretica;
3. 18 water chemistry variables;
4. concentrations of nine metals in 2-cm tips of Rhynchostegium at all sites and of Amblystegium and Fontinalis at one site each.

A decrease in the amounts of these mosses occurred in winter at most sites, the effect being most pronounced with Amblystegium. Nevertheless the majority of plants which remained had healthy shoots suitable for sampling for metal analysis at all times of year. There were marked temporal changes in the concentrations of metals in the 2-cm tips at each site, but few of these appeared to be related to seasonal events. The most plausible was for Pb in Rhynchostegium at a main river site, where increased accumulation in winter was probably an indirect effect of other chemical differences in the water during a period of high flows. Provided healthy shoots were available, there was no indication of seasonal differences in metal accumulation resulting from features of the mosses themselves.     

Accumulation of heavy metals by aquatic mosses. 1: Fontinalis antipyretica Hedw.

An account is given of methods developed to monitor heavy metals in rivers by measuring the concentration of these metals in Fontinalis antipyretica Hedw. Key features of the standard method recommended include the harvesting of materials from microhabitats with fast current speeds wherever possible, thorough washing in field and laboratory, use of terminal 2-cm lengths of shoot, drying at 105°C and digestion in 2 M HNO₃. In order to establish the extent to which this species is useful and to provide baseline data with which others can compare their own observations, samples of moss, water and sediments were harvested for analysis from 52 different sites in northern England and Belgium. Significant positive correlations were obtained between Cu and Zn in 2-cm tips and in both (total) water and sediment, but in the case of Cd and Pb only between 2-cm tips and sediment. Multiple stepwise regression was used to quantify the apparent influence of environmental variables. For instance, with Pb in the moss as the dependent variable, significant influences were found for Zn in the moss (+ve) aqueous Mn (+ve) and filtrable reactive phosphate (?ve). Variables which were significant were incorporated in each case into equations to predict the concentration of metal that would be expected if allowance was made for the concentrations of all these variables at each site. In the case of Pb, r² = 0.075 for metal in moss versus aqueous metal, whereas r² = 0.879 for metal in moss versus the predicted value for metal in moss. This suggests that the lack of correlation between Pb in moss and Pb in water was probably due largely to the influence of other variables. For Cd, the difference was less: r² = 0.013 and r² = 0.47, respectively. A principal components analysis was also carried out, with measurements of water and moss as the variables ordinated. An example is given of the use of the moss to monitor intermittent Zn pollution in R. Wear.     

Interactions of lichens with heavy metals

Recent developments in knowledge about the interactions between lichens and heavy metals at different levels, from populations to cells and from ecology to molecular biology are reviewed. Sources of heavy metals, mechanisms of heavy metal accumulation and detoxification by lichens are discussed. Special emphasis is placed on ultrastructural changes as well as physiological parameters such as membrane integrity, pigment composition, chlorophyll a fluorescence, photosynthesis, respiration, contents of ATP, amino acids, ergosterol, ethylene, non-protein thiols, activity of antioxidant enzymes and expression of stress proteins.     

Interspecific differences in metal bioaccumulation and plant-water concentration ratios in five aquatic bryophytes

We studied the capacity of five species of aquatic bryophyte to accumulate metals, and the relationship between plant metal content and water composition, on the basis of 170 samples taken from 32 rivers in Galicia (NW Spain). In all cases, only the final two centimetres of the apex were analysed. Scapania undulata was the species with the highest accumulatory capacity, and Fissidens polyphyllus was that with the lowest. Fontinalis antipyretica, Rhynchostegium riparioides and Brachythecium rivulare displayed intermediate capacities for metal accumulation, but showed a broader range of variation in body concentration in comparison with similar contamination levels. This resolution capacity, together with a greater resistance to pollution and, in the study region, a wider distribution and higher abundance, suggests that the latter two species are the most useful for bioindication studies. Bioaccumulation factors were high for all metals studied, tending to increase with increasing body concentration but decreasing with increasing water concentration. The relationship between metal in plant and filtrable metal in water was low, but statistically significant for all the metals studied except Co in F. antipyretica and Cd, Pb and Co in S. undulata, F. polyphllyllus and B. rivulare. The influence of physical and chemical variables of the water on bioaccumulation was evaluated using step-wise multiple correlation analysis. Bioaccumulation is largely governed by physical and chemical factors, by the concentration of metal in the water and by the bioaccumulation factor of the bryophyte species. Sulphate concentration, pH and to a lesser extent nitrite, ammonia and FRP (filtrable reactive phosphate) appear to be the most important physical and chemical variables governing metal bioavailability.     

The recovery of heavy metals using encapsulated microbial cells

We prepared capsules containingSaccharomyces cerevisiae andZoogloea ramigera cells for the removal of lead (II) and cadmium ions. Microbial cells were encapsulated and cultured in the growth medium. TheS. cerevisiae cells grown in the capsule did not leak through the capsule membrane. The dried cell density reached to 250 g/l on the basis of the inner volume of the 2.0 mm diameter capsule after 36 hour cultivation. The dry whole cell exopolymer density of encapsulatedZ. ramigera reached to 200 g/L. The capsule was crosslinked with triethylene tetramine and glutaric dialdehyde solutions. The cadmium uptake of encapsulated whole cell exopolymer ofZ. ramigera was 55 mg Cd/g biosorbent. The adsorption line followed well Langmuir isotherm. The lead uptake of the encapsulatedS. cerevisiae was about 30 mg Pb/g biomass. The optimum pH of the lead uptake using encapsulatedS. cerevisiae was found to be 6. Freundlich model showed a little better fit to the adsorption data than Langmuir model. 95 percent of the lead adsorbed on the encapsulated biosorbents was desorbed by the 1 M HCl solution. The capsule was reused 50 batches without loosing the metal uptake capacity. And the mechanical strength of the crosslinked capsule was retained after 50 trials.     

Avoidance response of Midge Larvae (Chironomus Tentans) to sediments containing heavy metals

Avoidance reactions of chironomid larvae to contaminated sediment taken from a heavy metal impacted lake were studied. Heavy metal levels in the test sediment ranged from background of 0.6 parts per million (ppm) cadmium, 77 ppm zinc and 17 ppm chromium to a maximum of 1,029 ppm cadmium, 17,262 ppm zinc and 2,106 ppm chromium. A linear relationship was established between cadmium and zinc levels in the sediment and avoidance by chironomids.An approximate threshold avoidance of metals in the sediment was determined to be between 213–422 ppm cadmium, 4385–8330 ppm zinc and 799–1513 ppm chromium.Supported by NIH Training Grant Number 5T01-ES00071 from National Institute of Environmental Health Sciences and in part by an NSF (RANN) Grant Number GI-35106.Purdue University Agricultural Experiment Station, Jour. No. 6474.     

Factors affecting tissue distribution of heavy metals

Metal distribution in an organism at any one time is a resultant of many extrinsic and intrinsic factors. Improved analytic methodology has made it feasible to obtain highly sensitive determinations for many metals in a single sample. Thus, it is now feasible to examine patterns of metal distribution. We report on a study of the effect of age on metal patterns in the common tern,Sterna hirundo, a fisheating seabird. We contrast the levels of nine metals in the liver of adult and young terns and compared these with levels in tern eggs. Unlike many previous studies, adults did not have significantly higher levels of metals, although for most metals, levels in eggs were significantly lower than liver levels of young and adults. The intermetal correlations showed more significant positive correlations for adults and eggs than for chicks, the latter showing instead a correlational chaos, probably reflecting the immaturity of their physiologic defense mechanisms and the absence of dynamic equilibrium.     

Modulation of synaptic events by heavy metals in the central nervous system of mollusks

Summary 1. The effects of heavy metals (Pb²⁺, Hg²⁺, and Zn²⁺) on synaptic transmission in the identified neural network ofHelix pomatia L. andLymnaea stagnalis L. (Gastropoda, Mollusca) were studied, with investigation of effects on inputs and outputs as wells as on interneuronal connections.2. The sensory input running from the cardiorenal system to the central nervous system and the synaptic connections between central neurons were affected by heavy metals.3. Lead and mercury (10^–5–10^–3 M) eliminated first the inhibitory, then the excitatory inputs running from the heart to central neurons. At the onset of action lead increased the amplitude of the excitatory postsynaptic potentials, but blockade of sensory information transfer occurred after 10–20 min of treatment.4. The monosynaptic connections between identified interneurons were inhibited by lead and mercury but not by zinc. Motoneurons were found to be less sensitive to heavy metal treatment than interneurons or sensory pathways.5. The treatment with Pb²⁺ and Hg²⁺ often elicited pacemaker and bursting-type firing in central neurons, accompanied by disconnection of synaptic pathways, manifested by insensitivity to sensory synaptic influences.6. Zn²⁺ treatment also sometimes induced pacemaker activity and burst firing but did not cause disconnection of the synaptic transmission between interneurons.7. A network analysis of heavy metal effects can be a useful tool in understanding the connection between their cellular and their behavioral modulatory influences.     

Use of aquatic macrophytes as a bioassay method to assess relative toxicity,uptake kinetics and accumulated forms of trace metals

Floating aquatic macrophytes such as the Lemnaceae have many attributes which commend their use in laboratory and field investigations to assess both the toxicity of substances and the quality of freshwater systems. As well as their more well known advantages of small size, relative structural simplicity, rapid growth and vegetative reproduction and genetically homogenous populations, they are also excellent accumulators of a number of metallic elements. This raises the possibility of the use of these aquatic macrophytes in water quality monitoring and also as laboratory bioassays for toxicity and uptake studies. Results are presented of a study of the comparative toxicity, uptake kinetics and accumulated forms of thallium and cadmium in the duckweed, Lemna minor and the role of this methodology in water quality monitoring and hazard evaluation are discussed.     

大型水生植物对重金属的富集与转移

通过野外调查和室内分析,研究了云南阳宗海南北两区域自然生长的17种水生植物的生长状况及植物和对应水样、根区底泥中重金属(As、Zn、Cu、Cd、Pb)的含量。结果表明:植物长势良好,未发现受害症状。水体As严重污染,Pb轻度污染,Zn、Cu和Cd均未超标。9种沉水植物同时对As、Zn、Cu、Cd、Pb的富集系数(植物全株重金属含量与水中该元素含量的比值)远大于1,具有共富集特征。在平均含As0.175mg/L的水中,金鱼藻、黑藻、小眼子菜、八药水筛全株As平均含量分别为(150±7.3)、(179±35)、(92±31)、(265±21)mg/kg(干重),对As具有较强富集能力;对于8种湿生和挺水植物,北部采样点的喜旱莲子草、田栖稗、细叶小苦荬和长芒稗对As,长芒稗、细叶小苦荬、圆果雀稗、水蓼和风车草对Cd,海芋和圆果雀稗对Zn的富集系数(植物地上部重金属含量与底泥中该元素含量的比值)以及圆果雀稗对Cd和Zn转移系数(植物地上部重金属含量与根中该元素含量的比值)均大于1。聚类分析结果表明,金鱼藻、黑藻、八药水筛、小眼子菜、穗状狐尾藻5种水生植物同时对As、Zn、Cu、Cd、Pb具有较强的吸收和富集能力,在重金属复合污染水体修复中具有较大潜力。     

Stress response in two strains of the aquatic hyphomycete <Emphasis Type="BoldItalic">Heliscus lugdunensis</Emphasis> after exposure to cadmium and copper ions

Biochemical responses to cadmium (Cd²⁺) and copper (Cu²⁺) exposure were compared in two strains of the aquatic hyphomycete (AQH) Heliscus lugdunensis. One strain (H4-2-4) had been isolated from a heavy metal polluted site, the other (H8-2-1) from a moderately polluted habitat. Conidia of the two strains differed in shape and size. Intracellular accumulation of Cd²⁺ and Cu²⁺ was lower in H4-2-4 than in H8-2-1. Both␣strains synthesized significantly more glutathione (GSH), cysteine (Cys) and γ-glutamylcysteine (γ-EC) in the presence of 25 and 50 μM Cd²⁺, but quantities and rates of synthesis were different. In H4-2-4, exposure to 50 μM Cd²⁺ increased GSH levels to 262% of the control; in H8-2-1 it increased to 156%. Mycelia of the two strains were analysed for peroxidase, dehydroascorbate reductase, glutathione reductase and glucose-6-phosphate dehydrogenase. With Cd²⁺ exposure, peroxidase activity increased in both strains. Cu²⁺ stress increased dehydroascorbate reductase activity in H4-2-4 but not in H8-2-1. Dehydroascorbate reductase and glucose-6-phosphate dehydrogenase activities progressively declined in the presence of Cd²⁺, indicating a correlation with Cd²⁺ accumulation in both strains. Cd²⁺ and Cu²⁺ exposure decreased glutathione reductase activity.     

Distribution of metals during digestion by cutthroat trout fed benthic invertebrates contaminated in the Clark Fork River, Montana and the Coeur d'Alene River, Idaho, U.S.A., and fed artificially contaminated Artemia

The concentrations of essential amino acids in three, undigested invertebrate diets collected from the Clark Fork River (CFR) for cutthroat trout were similar to each other, but were c. 25–75% less than Artemia that were exposed to a mixture of arsenic, copper, cadmium, lead and zinc in the laboratory. The Artemia diet appeared less palatable and the texture, quantity and appearance of the intestinal contents differed between fish fed the Artemia and CFR diets. The Pb% in the fluid fraction of the intestinal contents was greater for the Artemia (29%) than for the CFR diets (10–17%), and the Cu% in the amino acid plus metal fraction of the intestinal contents was greater for the Artemia (78%) than for two of the three CFR diets (67% and 70%). Intestinal contents of fish fed invertebrate diets collected from various sites on the Coeur d'Alene River (CDA), Idaho, were similar in texture, quantity, and appearance. For fish fed the CDA diets, differences in the distribution of metals among fractions of the digestive fluids appeared to be related to concentrations of metals in the invertebrate diets. Pb% was lowest of all metals in the fluid portion of the intestinal contents. However, >80% of all metals in the hind gut were associated with the particulate fraction where they may still be available for uptake through pinocytosis.     

Accumulation, depuration and distribution of cadmium and zinc in the green-lipped mussel Perna viridis (Linnaeus) under laboratory conditions

Ecotoxicological tests were conducted in the green-lipped mussel Perna viridis under laboratory conditions. Different rates of accumulation and depuration in soft tissues are found and this might be due to different mechanisms of metal binding and regulation. At the end of depuration, Cd levels in soft tissues of P. viridis were 10–30 times higher than before exposure, while Zn levels in soft tissues were almost similar to levels before exposure. These results indicate that P. viridis is a good biomonitoring organism for Cd but Zn levels might be actively regulated. It remains uncertain whether P. viridis is a good biomonitoring organism of environmental Zn contamination. However, the positive patterns, although different rates, of accumulation and depuration for Cd and Zn support the use of P. viridis as a biomonitoring agent for such metals.     

The concentration of cadmium,lead, copper and zinc inChironomus gr.thummi larvae (Diptera,Chironomidae) with deformedversus normal menta

The concentrations of Cd, Pb, Cu and Zn inChironomus gr.thummi were determined for 4th instar larvae from the polluted Dyle River, tributary of the Scheldt River (Belgium). Comparison was made between larvae with deformed and normal menta. Deformed larvae showed higher overall metal concentrations than normal larvae. Especially Pb and Cu had higher concentrations in deformed larvae (16.22 mg kg^–1 dry weight and 39.66 respectively) than in normal larvae (12.80 mg kg^–1 dry weight and 35.70 respectively). No significant differences were found in the concentrations of Cd and Zn (mean [Cd] = 0.81 mg kg^–1 dry weight and mean [Zn] = 313.12 mg kg^–1 dry weight). There was no difference between the two larval groups as far as total length, dry weight and developmental stage of the imaginal discs are concerned.     

羽衣甘蓝对镉的耐性和富集特征研究

以观赏绿化植物羽衣甘蓝(Brassica oleracea L.var.acephala DC.)为试验材料,采用盆栽试验,研究其对镉的耐性和富集特征,探讨羽衣甘蓝对镉污染土壤生物修复的可行性。结果显示:(1)随着镉处理浓度的增加,羽衣甘蓝干重呈先升高后降低的趋势,20~80mg·kg-1镉处理能促进植株的生长,100~120mg·kg-1镉处理虽然显著抑制了根系的生长,但是促进了地上部的生长,整体而言对全株生长无明显影响,表明羽衣甘蓝对镉有较强的耐性,且地上部的耐性高于根系。(2)所有镉处理下,羽衣甘蓝叶片的SOD、POD和APX活性较高,MDA含量和电解质渗漏率与对照无差异;而镉处理浓度高于80mg·kg-1时,根系的SOD、CAT和APX活性显著降低,MDA含量和电解质渗漏率显著升高,引起严重的膜脂过氧化伤害,这可能是羽衣甘蓝地上部的镉耐性高于根系的原因之一。(3)羽衣甘蓝地上部的镉含量高于根系,且随着镉处理浓度的增加均逐渐增加,在镉处理浓度为120mg·kg-1时达到最大值,分别为50.15mg·kg-1(根系)和52.01mg·kg-1(地上部);植株对镉的转运系数大于1,地上部镉富集量高于根系,地上部最大富集量为每株343.19μg。研究表明,羽衣甘蓝对镉有很强的耐性和富集、转运能力,是一种良好的修复镉污染土壤的观赏绿化植物资源。     

Accumulation,regulation and toxicity of copper,zinc, lead and mercury in Hyalella azteca

Zinc, lead and mercury accumulation in the amphipod Hyalella azteca increases with increasing exposure to metals. During 10 week chronic toxicity tests, metal accumulated at the highest non-toxic/lowest toxic concentration was 126/136 µg Zn g^–1, 7.1/16 µg Pb g^–1 and 56/90 µg Hg g^–1 dry weight. Concentrations of lead and mercyry in control animals were substantially lower (1.3 µg Pb g^–1 and 0.4 µg Hg g^–1), but concentrations of zinc in controls (74 µg g^–1) were about one half those of the lowest toxic concentration. Copper was completely regulated. Accumulated copper concentrations after 10 weeks exposure to all waterborne copper concentrations resulting in less than 100% mortality were not significantly different from controls (79 µg g^–1). Lead and mercury concentrations in wild H. azteca should be useful indicators of potential toxicity. Zinc accumulation may also be a useful indicator of zinc toxicity, but careful comparison with control or reference animals is necessary because of the small differences between toxic and control concentrations. Copper is not accumulated by H. azteca under chronic exposure conditions and body burdens of field animals cannot be used as an indicator of exposure or potential toxic effects. Short term exposures to copper, however, result in elevated copper concentrations in H. azteca, even at concentrations below those causing chronic toxicity. Short term bioaccumulation studies might, therefore, provide a useful indication of potential chronic copper toxicity.     

Effect of cations,including heavy metals,on cadmium uptake by Lemna polyrhiza L.

Cations, including calcium, magnesium, potassium, sodium, copper, iron, nickel and zinc, inhibited (up to 40%) extracellular binding and intracellular uptake of cadmium by Lemna polyrhiza in solution culture. Test plants showed a high capacity of extracellular cadmium binding which was competitively inhibited by copper, nickel and zinc; however, calcium, magnesium and potassium caused non-competitive inhibition. Iron and sodium increased K _m and decreased V _max, thereby causing mixed inhibition of extracellular binding. Intracellular cadmium uptake displayed Michaelis-Menten kinetics. It was competitively inhibited by calcium, magnesium, iron, nickel and zinc. Monovalent cations (sodium and potassium) caused non-competitive and copper caused mixed inhibition of intracellular cadmium uptake. Thus, high levels of cations and metals in the external environment should be expected to lower the cadmium accumulation efficiency of L. polyrhiza.